High efficiency multistep sinewave synthesizer
First Claim
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1. A multistep inverter for converting dc power to ac power comprising:
- primary inverter means for converting a source of dc power to an intermediate ac power signal;
a plurality of secondary inverter means, each having first and second output lines, for converting the intermediate ac power signal, in response to a control signal, to one of three output voltages appearing across the first and second output lines;
a positive voltage +V, a zero voltage 0V, or a negative voltage -V;
the plurality of secondary inverter means being stacked together in series circuit relationship so that the first output line of a 1st secondary inverter means is connected to one side of a load, the second output line of the 1st secondary inverter means is connected to the first output line of a 2d secondary inverter means, the second output line of the 2d secondary inverter means is connected to the first output line of a 3d secondary inverter means, and so on for n different secondary inverter means, where n is an integer of at least two, with the second output line of the nth secondary inverter means being connected to the other side of the load; and
control means for generating the control signal applied to each of the plurality of secondary inverter means in a way that combines select combinations of the +V, 0V, and -V outputs from the plurality of secondary inverter means in series across the load so that the signal applied across the load approximates a sine wave.
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Abstract
A multistep inverter uses multiple inverter H-bridges connected in series to piecewise approximate a sine wave. The inverter H-bridges are bypassed or switched into service as required for sinewave synthesis. After a step is switched in, it creates its portion of the sine wave. Each step is further smoothed using pulse width modulation which leads to a smoother sine wave with the consequent advantages of lower distortion, smaller and lighter filtering circuits, and lower conversion losses during transistor switching.
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Citations
10 Claims
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1. A multistep inverter for converting dc power to ac power comprising:
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primary inverter means for converting a source of dc power to an intermediate ac power signal; a plurality of secondary inverter means, each having first and second output lines, for converting the intermediate ac power signal, in response to a control signal, to one of three output voltages appearing across the first and second output lines;
a positive voltage +V, a zero voltage 0V, or a negative voltage -V;the plurality of secondary inverter means being stacked together in series circuit relationship so that the first output line of a 1st secondary inverter means is connected to one side of a load, the second output line of the 1st secondary inverter means is connected to the first output line of a 2d secondary inverter means, the second output line of the 2d secondary inverter means is connected to the first output line of a 3d secondary inverter means, and so on for n different secondary inverter means, where n is an integer of at least two, with the second output line of the nth secondary inverter means being connected to the other side of the load; and control means for generating the control signal applied to each of the plurality of secondary inverter means in a way that combines select combinations of the +V, 0V, and -V outputs from the plurality of secondary inverter means in series across the load so that the signal applied across the load approximates a sine wave. - View Dependent Claims (2, 3)
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4. A multistep synthesizer for converting dc power to ac power comprising:
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a primary inverter circuit that converts a source of dc power to an intermediate ac power signal; a transformer having primary and secondary windings, the intermediate ac power signal being applied to the primary winding; a plurality of secondary rectifier circuits, each connected to one of the secondary windings of the transformer, each secondary rectifier circuit having means for rectifying an ac signal received through the respective secondary winding to provide an intermediate dc voltage; a plurality of secondary bridge circuits, each secondary bridge circuit being connected to a respective one of the plurality of secondary rectifier circuits, each secondary bridge circuit having first and second output lines, each secondary bridge circuit having switches which, in response to a control signal, convert the intermediate dc voltage generated by the secondary rectifier circuit to one of three output voltages which appear across its first and second output lines;
a positive voltage +V, a zero voltage 0V, or a negative voltage -V; andwherein the plurality of secondary bridge circuits are stacked together so that the first output line of a 1st secondary bridge is connected to one side of a load, the second output line of the first bridge circuit is connected to the first output line of a 2d secondary bridge circuit, the second output line of the 2d secondary bridge circuit is connected to the first output line of a 3d secondary bridge circuit, and so on, for n different secondary bridge circuits, where n is an integer of at least two, with the second output line of the nth secondary bridge circuit being connected to the other side of the load; wherein the +V, 0V, and -V outputs from the plurality of secondary bridge circuits are combined in series across the load so that the signal applied across the load approximates a specified wave shape. - View Dependent Claims (5, 6, 7, 8, 9)
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10. A method of synthesizing an ac waveform having a desired waveshape from a source of dc power comprising:
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converting the source of dc power to an intermediate ac power signal; coupling the intermediate ac power signal through a transformer to a plurality of secondary windings of the transformer; rectifying the ac signal at each secondary winding of the transformer to produce a rectified secondary power signal; converting each rectified secondary power signal to one of three output voltages;
a positive voltage +V, a zero voltage 0V, or a negative voltage -V, wherein the one of three voltages appears across first and second output lines of each of a plurality of switched bridged circuits;stacking the switched bridged circuits in a series circuit relationship across a load by connecting the first output line of a 1st secondary inverter to one side of the load, connecting the second output line of the 1st secondary inverter to the first output line of a 2d secondary inverter, connecting the second output line of the 2d secondary inverter to the first output line of a 3d secondary inverter, and so on for n different secondary inverters, where n is an integer of at least two, and connecting the second output line of the nth secondary inverter to the other side of the load; and combining selected combinations of the +V, 0V, and -V outputs from the plurality of switched bridged circuits connected in series across the load so that the signal applied across the load approximates the desired waveshape.
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Specification